I haven't seen the movie, but my first impression would be that they're bf/gf, and the girl says "if you don't stop playing video games, I'll put naked pictures of myself up on the internet." and he tries to call her bluff... and we watch.

Really there are only two options... #1. It's her brother in which case that is creepy. And #2 it's her brother in which case it's creepy. I suppose there is a 3rd option but you guys aren't ready for that yet.

Hm, from what I have gathered, there are only two plausible theories
1. It's her brother, in which case, he should GTFO of the room
2. Boyfriend. if so, apparently, he doesnt mind his gf posing nude vidoes on the net, either way, the guy needs to reconsider his position on love.

Err, heh, ambiguity. By "knock it" I don't mean masturbation, I was using the phrase instead to refer to the act of mocking your taste in pornography. That was a bad phrase to use in a comment about porn, lol.